Perl output successive string from array - arrays

Question

I have an array I can print out as "abcd" however I am trying to print it as "a>ab>abc>abcd". I can't figure out the nested loop I need within the foreach loop I have. What loop do I need within it to print it this way?
my $str = "a>b>c>d";
my #words = split />/, $str;
foreach my $i (0 .. $#words) {
print $words[$i], "\n";
}
Thank you.

Answer 1

You had the right idea, but instead of printing the word at position i, you want to print all the words between positions 0 and i (inclusive). Also, your input can contain multiple strings, so loop over them.
use warnings;
while (my $str = <>) { # read lines from stdin or named files
chomp($str); # remove any trailing line separator
my #words = split />/, $str; # break string into array of words
foreach my $i (0 .. $#words) {
print join '', #words[0 .. $i]; # build the term from the first n words
print '>' if $i < $#words; # print separator between terms (but not at end)
}
print "\n";
}
There are many other ways to write it, but hopefully this way helps you understand what's happening and why. Good luck!

Answer 2

one liner:
perl -e '#a=qw(a b c d); for(#a) {$s.=($h.=$_).">"} $s=substr($s,0,-1);print $s'

Answer 3

I would do it like this:
#!/usr/bin/perl
use strict;
use warnings;
my $str = "a>b>c>d>e>f>g";
my #words = split />/, $str;
$" = '';
my #new_words;
push #new_words, "#words[0 .. $_]" for 0 .. $#words;
print join '>', #new_words;
A few things to explain.
Perl will expand array variables in a double-quoted string. So something like this:
#array = ('x', 'y', 'z');
print "#array";
will print x y z. Notice there are spaces between the elements. The string that is inserted between the elements is controlled by the $" variable. So by setting that variable to an empty string we can remove the spaces, so:
$" = '';
#array = ('x', 'y', 'z');
print "#array";
will print xyz.
The most complex line is:
push #new_words, "#words[0 .. $_]" for 0 .. $#words;
That's just a compact way to write:
for (0 .. $#words) {
my $new_word = "#words[0 .. $_]";
push #new_words, $new_word;
}
We iterate across the integers from zero to the last index in #words. Each time around the loop, we use an array slice to get a list of elements from the array, convert that to a string (by putting it in double-quotes) and then push that string onto #new_words.

Answer 4

This is what I ended up with, It's the only way I could understand and get the output I was looking for.
use strict;
use warnings;
my $str = "a>b>c>d>e>f>g";
my #words = split />/, $str;
my $j = $#words;
my $i = 0;
my #newtax;
while($i <= $#words){
foreach my $i (0 .. $#words - $j){
push (#new, $words[$i]);
}
if($i < $#words){
push(#new, ">");
}
$j--;
$i++;
}
print #new;
This output "a>ab>abc>abcd>abcde>abcdef>abcdefg"