my $description = "windows and linux and solaris";

$os = $1 if ( $description =~ /(windows)/i );
$os = $1 if ( $description =~ /(linux)/i );
$os = $1 if ( $description =~ /(solaris)/i );
print $os;

$os = $1 if $description =~ /(windows|linux|solaris)/i;
print "   $os\n";