What if the file is actually a directory? I have never tried it but the documentation for unlink gives some warnings.

How about:

for my $file (qw(files.txt data.txt)) {
    unlink $file if -f $file;
    die "Unable to unlink '$file': $!" if -e $file;
}
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Update: If the file tests are different then it would die after not attempting to delete a directory and $! would not be set. In that case -f is false and -e is true. If I make them the same that won't happen.

for my $file (qw(files.txt data.txt)) {
    unlink $file if -f $file;
    die "Unable to unlink '$file': $!" if -f $file;
}
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Better yet; do an unlink or warn.

for my $file (qw(files.txt data.txt)) {
    if ( -f $file) {
       unlink $file or warn "Unable to unlink '$file': $!";
    }
}
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