Your post could use a little improvement, such as wrapping input in <code> tags and clearly specifying your desired output - I can't really follow your spec. See How do I post a question effectively?.

I think you can meet your spec using:

#!/usr/bin/perl -w
use strict;

$_ = 'childhe.com/pas/ apstpldr.dll.html? affid=177194&uid=& guid=4E83
+C7975FCD4 4B091226646F461D89 1/pas/apstpldr.dll .html?affid=177194 &u
+id=&guid= 4E83C7975FCD44B091 226646F461D89';
s/\?.*?(?=\/|$)//g;
print;
[download]

which outputs:

childhe.com/pas/ apstpldr.dll.html/pas/apstpldr.dll .html

YAPE::Regex::Explain interprets this regular expression as:

The regular expression:

(?-imsx:\?.*?(?=/|$))

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  \?                       '?'
----------------------------------------------------------------------
  .*?                      any character except \n (0 or more times
                           (matching the least amount possible))
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    /                        '/'
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
[download]

See perlretut for more information on regular expressions.