A different example, maybe it will help. My script gets used by others on different platforms. Since Windows/DOS doesn't glob the way *nix does, this module isn't necessary on *nix.

# This BEGIN block avoids including File::DosGlob::Param for non-windo
+ws systems
BEGIN
{
  if ( $^O =~ /win/i )
  {
    require File::DosGlob::Param;
    import  File::DosGlob::Param qw( dosglob );
  }
}

# convert filename wildcards to actual filenames
if ( $^O =~ /win/i ) # only if DOS
{
  if ( exists( $INC{'File/DosGlob/Param.pm'} ) ) # only if loaded
  {
    dosglob( "Array_Ref" => \@ARGV, 
             "Remove_Empty_Matches" => 1,
             "Warn_On_Empty_Matches" => 1 );
  }
  END
  {
    if ( ( $^O =~ /win/i )
     and not exists( $INC{'File/DosGlob/Param.pm'} ) )
    {
      warn "Consider installing module File::DosGlob::Param...\n";
    }
  }
}
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