Working, (loosely) tested code:

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

sub grep_dir_of_logs {
  die unless @_ == 4;
  my ( $dir, $sel_user, $sel_host, $sel_mod ) = @_;

  $_ = lc $_ for $sel_user, $sel_host, $sel_mod;

  my $inside_brackets_re = qr{  \[  ( [^[]+ )  \]  }msx;
  my $line_re = qr{
    \A
      $inside_brackets_re
      $inside_brackets_re
      $inside_brackets_re
      $inside_brackets_re
      \s*
      (\S.*?)
      \s*
    \z
  }msx;

  opendir my $dh, $dir
    or die "Can't opendir '$dir': $!\n";
  my @files = grep { !/user.log/ } readdir $dh;
  closedir $dh;

  foreach my $fname ( @files ) {
    my $filename = "$dir/$fname";
    next if -d $filename;

    open my $fh, $filename
      or die "Error opening '$filename': $!";

    while (<$fh>) {
      chomp;

      my ( $date_string, $host, $user, $module, $message )
        = /$line_re/ or die;

      next if $sel_user ne 'all' and $sel_user ne lc $user;
      next if $sel_host ne 'all' and $sel_host ne lc $host;
      next if $sel_mod  ne 'all' and $sel_mod  ne lc $module;

      print "Passed: $_\n";
    }

    close $fh
      or warn "Error closing '$filename': $!";
  }

  return;
}

use IO::Prompt;
grep_dir_of_logs(
  './logs/commonlogs',
  prompt('User  : '),
  prompt('Host  : '),
  prompt('Module: '),
);
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