use strict;
use warnings;

my @text = (
    "So, I went to the store and I wanted to buy a book, but it was too expensive, so\nI went home",
    "So, I went to the store and I wanted to buy a book, but it was\ntoo expensive, so I went home",
    "So, I went to the store and I wanted to\nbuy a book, but it was too expensive, soI went home",
    );

my $query = 'store';

foreach my $teststr ( @text )
{
    $teststr =~ m/
                    $query      # query string
                    [^,]*       # zero or more chars that are not a comma
                    ,           # followed by one comma
                    (           # begin capture
                        [^,]*   # zero or more chars that are not a comma
                    )           # end capture
                    ,           # followed by one comma
                /x;

    print "found: [$1]\n" if $1;
}

##</code><code>##

found: [ but it was too expensive]
found: [ but it was
too expensive]
found: [ but it was too expensive]