I'm still not sure what you're trying to achieve here, cause your grep returns the PATTERNs which matched.

Are those patterns simple words? If yes you could consider constructing an or-regex:

  DB<100> @patterns=qw#one two three#
 
  DB<101> $str="one two"
 
  DB<102> $re=join "|",@patterns
 
  DB<103> print $str =~ m/($re)/g
onetwo
[download]

UPDATE:

just noticed there are still subtle differences:

  DB<106> $str="two one two"
 
  DB<107> print $str =~ m/($re)/g
twoonetwo
  DB<108> print grep {$str=~/$_/} @patterns
onetwo
[download]