I needed to format some data for email confirmation messages, and needed to save the output in a variable instead of sending it straight to a file handle, plus I needed a variable format. After a detour through considering IO::Scalar (write will not work on tied file handles) and a suggestion to use IPC::Open2 (interesting, but yuck), I found what I needed in perlfaq5 and a re-read of perlform in the form of the '~~' format attribute (you won't find it by searching for '~~' either), the formline function, and the $^A variable.

This was good enough for me, if you want to combine left and right justification of fields, you can set up a hash of field names, and that's left as an exercise :)

my %formats; # cache for format types sub format_items { # Key for what 'type' of format we have my $type = shift; # Data to format in a list of hashrefs my $items = shift; # Get cached format or construct new one # We could just use the '$line' argument as the hash # key, but I'd rather label them, and it fit better with # what I was doing at the time. my $fmt = $formats{$type} || do { # format line is in form "key1:length1;key2:length2;etc." my $line = shift; my %lengths = map { split /:/ } my @fields = split /;/, $line; s/:.*// for @fields; my $picture = join " ", map { '^' . ("<" x ($lengths{$_}-1)) } @fields; $picture .= "~~\n"; $formats{$type} = [ \@fields, $picture ]; }; my ($fields, $picture) = @$fmt; $^A = ''; for my $href (@$items) { s/^\s+// for values %$href; # Warning: formline is destructive to the data in href # when using '~~' and '^' :-0 # But I don't need the data after this anyway :-) # If you have a lot of records, you might want to # process and return one record at a time. formline($picture, @$href{@$fields}); } return $^A; } my @data = ( {quantity=>1, description=>'Super Widget', price=>'$29.95'}, {quantity=>1, description=>'Really Great Product With A Real Long Description', price=>'$39.95'}, ); # Please don't blame me for the format spec :) my $format = "quantity:4;description:20;price:9"; my $formatted = format_items('NEW_ORDER', \@data, $format); print $formatted; print "\n"; @data = ( {quantity=>1, description=>'Super Widget', price=>'$29.95', status=>'SHIPPED'}, {quantity=>1, description=>'Really Great Product With A Real Long Description', price=>'$39.95', status=>'SHIPPED'}, ); $format = "quantity:4;description:20;price:9;status:10"; $formatted = format_items('SHIPPED_ORDER', \@data, $format); print $formatted; # OUTPUTS 1 Super Widget $29.95 1 Really Great Product $39.95 With A Real Long Description 1 Super Widget $29.95 SHIPPED 1 Really Great Product $39.95 SHIPPED With A Real Long Description