my $line = 'She was very absorbed in her homework.';
my $word = 'absorb';

$_=$line;
s/ ($word)//g;
print "\$1 is $1\n";
$_=$line;
s/ ($word)//i;
print "\$1 is $1\n";
$_=$line;
s/ ($word)//ig;
print "\$1 is $1\n";