grep { /x/ } @source;

##</code><code>##

grep( /x/, @source );

##</code><code>##

grep /x/, @source;

##</code><code>##

grep { my $x = $_;
       $x =~ s/\D//g;
       my $y = f( $x );
       ( $y > $x ) } @source;

##</code><code>##

grep s/\D//g && f( $_ ) > $_, @source;