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

while ( <DATA> ) {

    if ( $_ =~  m/^X(<.+>(?: X<.+?>){0,4})/ ) {

        my @matches = map { s/^<+\s*|\s*>+$//g; $_ } split m/\s+X/, $1;

        print join "--", @matches;
    }
    else {
        print STDERR "no matches.";
    }
}

__DATA__
X<$!> X<$ERRNO> X<$OS_ERROR>
X<< $< >> X<$UID> X<$REAL_USER_ID>
X<$;> X<$SUBSEP> X<SUBSCRIPT_SEPARATOR>