You should turn on 'use strict' and 'use warnings', this will help lead you to a better solution.

It seems your main problem might be that you are confusing the space character ' ' with the whitespace character class.

In a regex, '\s' matches not only the space character, but ANY whitespace character. See Whitespace.

Your substitutions like 's/\[/\s/' will fail because '\s' is only recognized as whitespace in a regex:

$ perl -wE 'my $str = "JA_PH"; $str =~ s/_/\s/; say $str'
Unrecognized escape \s passed through at -e line 1.
JAsPH
$ perl -wE 'my $str = "JA_PH"; $str =~ s/_/ /; say $str'
JA PH
[download]

Also, your regex for substituting whitespace with underscore will only match a whitespace character followed by a space character. I don't think this is quite what you meant.

$ perl -wE 'my $str = "Some text with  whitespace"; $str =~ s/\s /_/g;
+ say $str'
Some text with_whitespace
$ perl -wE 'my $str = "Some text with  whitespace"; $str =~ s/\s/_/g; 
+say $str'
Some_text_with__whitespace
$ perl -wE 'my $str = "Some text with  whitespace"; $str =~ s/\s+/_/g;
+ say $str'
Some_text_with_whitespace
[download]

Best,

Jim