I think I would rather explicitly extract whatever it was I was interested in rather than relying on a somewhat obscure feature of the split built-in:

c:\@Work\Perl\monks>perl -wMstrict -le
"$_ = qq{xxx ekey=foo bar \n xyzzy};
 ;;
 my (undef, $captured) = split(/ekey=(.+)/, $_);
 print qq{captured '$captured'};
 ;;
 my ($bagged) = $_ =~ m{ ekey= ([^\n]+) }xms;
 print qq{  bagged '$bagged'};
"
captured 'foo bar '
  bagged 'foo bar '
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