[StainlessS]

Originally Posted by johnmeyer

I get my wrist slapped by Gavino every time I use global variables.

And rightly so

The above Multi-instance function, provides unique named Functions and unique named Globals,
and so are safe to use in multi-instance, so long as below name is unique in the entire script, (multi-instance use in same script ok)
in this case I've just used "MX".
You cannot have two different multi-instance functions both using the same GIFunc name (ie 'MX')

GIFunc ="MX"                       # Function Name, Supply unique name for your multi-instance function.

With two instances produces these results:- (The RT_WriteFile() line uncommented)

DEBUG_MX_1.TXT

        Function Fn_MX_1(clip c1,clip c2,Bool Show,String Fmt) {
            c1
            n = current_frame
            If(Prev_MX_1 == n) {  # Cache failure, requested same frame again.
                RT_DebugF("%d ] Cache Failure",n,name="Fn_MX_1_DBUG: ")
            } Else If(Prev_MX_1 + 1 != n) { # Init OR Rewind OR User jumped about, dont you just hate users!
                if(n == 0) {
                    if(Prev_MX_1 == -666) {
                        RT_DebugF("%d ] Initialized to frame 0",n,name="Fn_MX_1_DBUG: ")
                    } else {
                        RT_DebugF("%d ] Rewind to frame 0",n,name="Fn_MX_1_DBUG: ")                
                    }                
                } else {
                    RT_DebugF("%d ] User Jumped About",n,name="Fn_MX_1_DBUG: ")                
                }
            }
            if(Show) {
                RT_Subtitle(Fmt,n, c1.RT_AverageLuma(n=n), c2.RT_AverageLuma(n=n))
            }
            Global Prev_MX_1=current_Frame                            # Previous frame (For next interation jump about detect)
            Return Last
        }
        #######################################
        # Unique Global Variables Initialization
        #######################################
        Global Prev_MX_1= -666 # Init vars, Prev = -666 forces initalize
        #######################################
        # Unique Runtime Call, GScriptClip must be a one-liner:
        #######################################
        ARGS = "c2,Show,Fmt"
        c1.GScriptClip("Fn_MX_1(last, "+ARGS+")", local=true, args=ARGS)

DEBUG_MX_2.TXT

        Function Fn_MX_2(clip c1,clip c2,Bool Show,String Fmt) {
            c1
            n = current_frame
            If(Prev_MX_2 == n) {  # Cache failure, requested same frame again.
                RT_DebugF("%d ] Cache Failure",n,name="Fn_MX_2_DBUG: ")
            } Else If(Prev_MX_2 + 1 != n) { # Init OR Rewind OR User jumped about, dont you just hate users!
                if(n == 0) {
                    if(Prev_MX_2 == -666) {
                        RT_DebugF("%d ] Initialized to frame 0",n,name="Fn_MX_2_DBUG: ")
                    } else {
                        RT_DebugF("%d ] Rewind to frame 0",n,name="Fn_MX_2_DBUG: ")                
                    }                
                } else {
                    RT_DebugF("%d ] User Jumped About",n,name="Fn_MX_2_DBUG: ")                
                }
            }
            if(Show) {
                RT_Subtitle(Fmt,n, c1.RT_AverageLuma(n=n), c2.RT_AverageLuma(n=n))
            }
            Global Prev_MX_2=current_Frame                            # Previous frame (For next interation jump about detect)
            Return Last
        }
        #######################################
        # Unique Global Variables Initialization
        #######################################
        Global Prev_MX_2= -666 # Init vars, Prev = -666 forces initalize
        #######################################
        # Unique Runtime Call, GScriptClip must be a one-liner:
        #######################################
        ARGS = "c2,Show,Fmt"
        c1.GScriptClip("Fn_MX_2(last, "+ARGS+")", local=true, args=ARGS)

I feel quite sure that the big G would not give you a hard time for using such an arrangement as above,
seeing as he was party to its conception.

EDIT: The unique calling code is below the actual unique functions.

EDIT: Produces this in DebugView on first frame

[4024] Fn_MX_1_DBUG: 0 ] Initialized to frame 0
[4024] Fn_MX_2_DBUG: 0 ] Initialized to frame 0