sub addrtoint { return( unpack( "N", pack( "C4", split( /[.]/,$_[0] 
                                                      ) ) ) ) };
sub inttoaddr { return( join( ".", unpack( "C4", pack( "N", $_[0] ) )
                                         ) ) };

my $ipinc = addrtoint( '1.2.3.4' );
$ipinc++;

print( inttoaddr( $ipinc ) . "\n" );