I think you getting confused with the trailing spaces and the whitespaces. Trailing spaces are the spaces that comes at the end of the last character. In your case "]" is the last character. Please look at the code below:

#!/usr/bin/perl

use strict;
use warnings;

my $str1 = "The tailing spaces example 1     "; ## spaces after 1
$str1 =~ s/\s+$//g;
my $str2 = "The tailing spaces example 2"; 
$str2 =~ s/\s+$//g;

print "Output 1:",$str1,"\n"; ## this removes the spaces after 1
print "Output 2:",$str1,"\n"; ## does nothing
print "Output 3:",$str1.$str2,"\n"; ## removes spaces and concatenates
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OUTPUT:

Output 1:The tailing spaces example 1
Output 2:The tailing spaces example 2
Output 3:The tailing spaces example 1The tailing spaces example 2
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Therefore, I would like to know what are you trying to do. If you want to remove the white spaces then you have to remove "$" from you substitution command i.e.:

$str1 =~ s/\s+//g;
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the the output will be as follows:

Output 1:Thetailingspacesexample1
Output 2:Thetailingspacesexample2
Output 3:Thetailingspacesexample1Thetailingspacesexample2
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