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Editorial Team
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Asked: 2026-05-28T13:42:46+00:00

In my perl progarm i have the following code: @alpha=(‘toM’,’jERRy’,’mickeY’,’MARio’); print sort{$a cmp $b}

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In my perl progarm i have the following code:

@alpha=('toM','jERRy','mickeY','MARio');
print sort{$a cmp $b} @alpha,'  "***MIDDLE STRING***"  ';

here it prints the

‘ “***MIDDLE STRING***” ‘

first and then the sorted @alpha list. Why it prints in reverse order, when

print "a","b";

prints

ab

in correct order. I googled for help but it speaks about “reverse” function/method of perl but i don’t use that function in my code. I found the answers irrelevant.

I guess it deals something with internal working of “print” function, using “stack” data structure, but I have no idea. Somebody help me out.

Thanks in advance…

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1 Answer

  1. Editorial Team
    print sort {$a cmp $b} @alpha,'  "***MIDDLE STRING***"  ';      #1
print sort {$a cmp $b} (@alpha,'  "***MIDDLE STRING***"  ');    #2

print (sort {$a cmp $b} @alpha), '  "***MIDDLE STRING***"  ';   #3
(print sort {$a cmp $b} @alpha), '  "***MIDDLE STRING***"  ';   #4

print ((sort {$a cmp $b} @alpha), '  "***MIDDLE STRING***"  '); #5

print sort {$a cmp $b} @alpha;                                  #6
print '  "***MIDDLE STRING***"  ';

print sort(@alpha), '  "***MIDDLE STRING***"  ';                #7
print sort({$a cmp $b} @alpha), '  "***MIDDLE STRING***"  ';    #8

    #1 and #2 are equivalent: sort is operating on a list containing all of the elements of @alpha plus the string, thanks to Perl’s automatic flattening of lists. You might be tempted to add some parentheses around sort (#3), but that doesn’t help you either, because it’s interpreted as a list of two elements (#4): the result of calling print, and the string. Thus the string will not be printed, because it has nothing to do with print.

    You could use an extra set of parentheses (#5) or split it up (#6), but knowing sort {$a cmp $b} @alpha is identical to sort @alpha, you can omit the block and the parentheses become straightforward (#7). And by the same rule, if you do need a comparison function, you can put both arguments to sort within parentheses, not separated by a comma (#8).

    I also like to define subs for different kinds of sorting, to make the code simpler to read:

    sub numerically { $a <=> $b }
sub backward { $b cmp $a }

print sort(numerically @array);    # Sort numerically ascending.
print sort(backward @array);       # Sort lexicographically descending.
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