print join(" ", sort {$a <=> $b} @char_count);
[download]

Read the error message. The error produced is:

Array found where operator expected at noname.pl line 6, at end of lin
+e
    (Missing operator before ?)
syntax error at noname.pl line 6, near "$b @char_count"
Execution of noname.pl aborted due to compilation errors.
[download]

then read the documentation.

Note too that use diagnostics; can help understand what is going on. Adding diagnostics gives the following message:

Array found where operator expected at noname.pl line 7, at end of lin
+e (#1)
    (S syntax) The Perl lexer knows whether to expect a term or an ope
+rator.
    If it sees what it knows to be a term when it was expecting to see
+ an
    operator, it gives you this warning.  Usually it indicates that an
    operator or delimiter was omitted, such as a semicolon.
    
    (Missing operator before ?)
syntax error at noname.pl line 7, near "$b @char_count"
Execution of noname.pl aborted due to compilation errors (#2)
    (F) Probably means you had a syntax error.  Common reasons include
+:
    
        A keyword is misspelled.
        A semicolon is missing.
        A comma is missing.
        An opening or closing parenthesis is missing.
        An opening or closing brace is missing.
        A closing quote is missing.
    
    Often there will be another error message associated with the synt
+ax
    error giving more information.  (Sometimes it helps to turn on -w.
+)
    The error message itself often tells you where it was in the line 
+when
    it decided to give up.  Sometimes the actual error is several toke
+ns
    before this, because Perl is good at understanding random input.
    Occasionally the line number may be misleading, and once in a blue
+ moon
    the only way to figure out what's triggering the error is to call
    perl -c repeatedly, chopping away half the program each time to se
+e
    if the error went away.  Sort of the cybernetic version of S<20
    questions>.
    
Uncaught exception from user code:
    syntax error at noname.pl line 7, near "$b @char_count"
Execution of noname.pl aborted due to compilation errors.
 at noname.pl line 7
[download]

Which actually has the hint you needed: "An opening or closing brace is missing.".