use strict;
use warnings;

my %keywords;
@keywords{
    'keyword1',
    'keyword2',
    'keyword3'
} = ();

while( <DATA> ){
    chomp;
    while( m/\b([\w'-]+)\b/g ) {
        print "'$_' contains keyword: $1\n" 
          if exists $keywords{ $1 };
    }
}
__DATA__
a line with keyword2 in it
a line with keyword1 and keyword3.
a line with no keywords.
keyword1 can start a line too.
and a line can end in keyword2