You need to start tracing the check_file subroutine. There is at least one questionable line in it:

    open FILE,$file || die "Cant open $file!\n";
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has a precedence problem. If the open fails then it will not execute the die (and we not not saying why the open failed). A better way is:

    open (FILE,$file) || die "Cant open $file: $!\n";
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or

    open FILE,$file or die "Cant open $file: $!\n";
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or even better

    open (my $fh, '<', $file) || die "Cannot open $file: $!";
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Then change the occurences of FILE to $fh.

By the way, the extra '\' are required since '\' is a special character in perl strings (as in many languages). In most cases you can use '\\' or '/' in a Windows filename path, and even mix them in the same path. You probably do not need that RE.