use strict;
use warnings;
use Tk;
use Tk::BrowseEntry;

my %CFG = ( 'target' => 'foobar' );

my $main = MainWindow->new();

my $entry = $main->BrowseEntry( -variable=>\$CFG{target}, );
$entry->grid( -row=>1, -column=>1, );
my $continue = $main->Button( -command=>\&continue, -text=>'run', );
$continue->grid( -row=>2, -column=>1, );

sub continue {
    warn "$CFG{target}\n";
    if ( $CFG{target} =~ s/bar//xms ) {
        warn "expecting this message\n";
    }
    warn "$CFG{target}\n";
}
MainLoop();