In addition to Zaxo's fix, you'll need to add ^ and $ if you want "FRAUD-REPORT###.CSV" to be the entire string.

foreach my $file (@filelist) {
   push(@curr, $1) if $file =~ /^(FRAUD-REPORT\d+\.CSV)$/i;
}
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Furthermore, you can simplify things a bit if you're trying to match the entire string (as per wazoox's post):

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

my @curr = grep /^FRAUD-REPORT\d+\.CSV$/, @filelist;
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