torgny has asked for the wisdom of the Perl Monks concerning the following question:

I would like to use perltidy but I cannot quite wrap my head around how continuation indentation works when it comes to certain statements.

Formatting the lines

if ($foofoofoofoofoo && $barbarbarbarbar && $bazbazbazbazbaz && $quuxq +uuxquuxquuxquux) { foo(); }
with perltidy using the default options of -l=80 -i=4 -ci=2, I would expect the program to output
if ( $foofoofoofoofoo && $barbarbarbarbar && $bazbazbazbazbaz && $quuxquuxquuxquuxquux ) { foo(); }
However, the actual result is
if ( $foofoofoofoofoo && $barbarbarbarbar && $bazbazbazbazbaz && $quuxquuxquuxquuxquux ) { foo(); }
That is, perltidy is breaking up the first line and indenting it with four spaces (actually, the number of spaces specified by the -i option) instead of two spaces. I have searched the ChangeLog of perltidy (which is otherwise very helpful in explaining changed behavior of the program) for an explanation but I haven't found other than that something seems to have changed between 2001 06 17 and 2001 10 16 which have the following, respectively:
if ($bigwasteofspace1 && $bigwasteofspace2 || $bigwasteofspace3 && $bigwasteofspace4) { bigwastoftime(); } if ( $opt_d || $opt_m || $opt_p || $opt_t || $opt_x || ( -e $archive && $opt_r ) ) { ( $pAr, $pNames ) = readAr($archive); }

My first thought was that perltidy is aligning the expression with the opening paren, but that does not seem to be the case, as replacing if with while yields

while ($foofoofoofoofoo && $barbarbarbarbar && $bazbazbazbazbaz && $quuxquuxquuxquuxquux ) { foo(); }

It may be noted that perltidy does not insert a space after the opening paren despite the the manual's claim that spaces within containers are always symmetric. In fact, while -pt=2 will remove the space before the closing paren, not even -pt=0 will insert a space after the opening paren.

Why is perltidy using indent-columns instead of continuation-indentation and why is the tightness not symmetric in these particular cases? What is it that I fail to understand? Is continuation-indentation used only for certain long lines and not for others?