sub file2sha1 {
    my $file=$_[0];
    return '' if -d $file; #have to find out if to prune when a directory is found that doesn't match the regex
    open my $f,"<$file";
    my $sha1 = Digest::SHA1->new;
    $sha1->addfile(*$f);
    return $sha1->hexdigest;
}

1. You should open the file in "binary" mode to work correctly.
2. You should verify that the file opened correctly.
3. *$f makes no sense because $f is a lexical variable that contains a reference to a filehandle.
4. You should probably use $sha1->digest instead which is half the size of $sha1->hexdigest.

sub file2sha1 {
    my $file = $_[ 0 ];
    return '' if -d $file; #have to find out if to prune when a direct
+ory is found that doesn't match the regex
    open my $f, '<:raw', $file or do {
        warn "Cannot open '$file' $!";
        return;
        };
    my $sha1 = Digest::SHA1->new;
    $sha1->addfile( $f );
    return $sha1->digest;
}
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