#!/usr/bin/perl
use 5.016;
use strict;
use warnings;

# 1039350

$_ = "  this is a number [12345]   ";

if(/^\s*(.+)\s*/){
    say "in outter 'if', \$1: $1";
    $_ = $1;
    if($1 =~ /\[(\d+)\]/){
           say "\t But in inner if, \$1 : $1";
       }
 }

=head output:

in outter 'if', $1: this is a number [12345]
         But in inner if, $1 : 12345

=cut