You didn't miss much, but I missed a single quote at the start of my list.

Change

my @cmd = ( "convert,
             ...
            ], $rrfile" );
[download]

to

my @cmd = ( "convert",
             ...
            ], $rrfile );
[download]

What you should put into @cmd is the list of arguments, and not a string containing that list.

... and now it tells me:

syntax error at ./IMTest33.pl line 22, near "]"
  (Might be a runaway multi-line [] string starting on line 10)
Execution of ./IMTest33.pl aborted due to compilation errors.
[download]

Guess I need some commas somewhere or...?

Here is your changed code with the syntax errors fixed:

#!/usr/bin/perl -w
#use Image::Magick; # you don't need that if you shell out to convert
use strict;

my $file="1251748705.jpg";
my $rfile="thumbnail.gif";
my $rrfile="thumbnail2.png";

my @cmd = ( "convert", # added the double quote here
            $rfile,
            qw[( +clone
                 -threshold -1
                 -virtual-pixel black
                 -spread 10
                 -blur 0x3
                 -threshold 50%
                 -spread 1
                 -blur 0x.7
               )
               +matte
               -compose Copy_Opacity
               -composite
            ], $rrfile ); # removed a double quote here


#system("convert -size 500x180  $file -auto-orient -thumbnail 250x90  
+ -unsharp 0x.5  $rfile");
print "About to run [@cmd]\n";
system(@cmd) == 0 or die "Couldn't launch [@cmd]: $!/$?";
[download]

This program compiles for me. As I don't have the convert executable, I can't tell you whether it does what it should.

For further reading, you might want to read perlop about the "Quotes and Quote-like Operators".