use strict; use warnings; will probably help you finding what's wrong. What's $1 supposed to be ? It looks like you're looking for $_ instead.

use strict;
use warnings; 

my @filelist=qw( FRAUD-REPORT01032006.CSV toto tata );
my @curr;

foreach my $file ( @filelist) {
    push @curr, $file if $file =~ /FRAUD-REPORT\d+\.CSV/i
}

sort @curr;
print "@curr";
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