Perl : getting an exact match from grep

Question

I am matching the contents of 2 arrays like this:

foreach $headerLine(@headerLines)
{
  if (grep { $headerLine =~ /$_/} @filterLines) 
  {
      #do something
  }
}

I need an exact match here, but ^$_$ does not work. How do I go about it?

Answer 1

You don't need a regex if you want an exact match.

if (grep { $headerLine eq $_ } @filterLines) 
{
    #do something
}

Your original problem was likely that $_ had special regex characters, and these are treated as regex syntax rather than matching those literal characters. For example, if $_ was ... it would match any three characters rather than the exact string ... . This also might result in an error if the variable didn't contain valid regex syntax (eg $_ = '(' ).

You can get around this with the \\Q...\\E quote literal construct:

if (grep { $headerLine =~ /^\Q$_\E$/} @filterLines) 
{
    #do something
}