You don't say whether the progressive number is per folder or for the whole run - I've gone for per-folder here - if you want for the whole run then change the hash
$num{$dir} to a scalar
$num instead.
#!/usr/bin/perl
use strict;
use warnings;
use File::Find;
use File::Copy;
#
# Set this to 0 to turn off printing which files it's moving.
#
my $verbose = 1;
my @dirs = qw(
Folder_1
Folder_2
Folder_3
Folder_4
);
my %num;
sub wanted {
if ( -f $_ ) {
my $dir = $File::Find::dir;
$num{$dir}++;
my $src = "$dir/$_";
my $target = "${dir}_$num{$dir}.jpg";
my $mv_msg = "move '$src' to '$dir/$target'";
if ( -f $target ) {
die "Can't $mv_msg: File already exists!\n"
}
else {
move( $_, $target ) || die "Can't $mv_msg: $!\n";
print "$mv_msg OK\n" if ($verbose);
}
}
}
File::Find::find( { wanted => \&wanted }, @dirs );
I'm also presuming here that you want them left in the same directory they were in - not moved up.