Are you sure your print statement is print @arr not print "@arr"? They have different default behavior for what gets printed between the elements...

% perl -le '@arr = 1..10; print @arr; print "@arr"'
12345678910
1 2 3 4 5 6 7 8 9 10
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If you really are getting an extra space using print @arr you might want to check the value of $, which is usually an empty string...

% perl -le '$, = ""; print 1..10' 
12345678910

% perl -le 'print 1..10' 
12345678910

% perl -le '$, = " "; print 1..10' 
1 2 3 4 5 6 7 8 9 10

% perl -le '$, = " abc "; print 1..10' 
1 abc 2 abc 3 abc 4 abc 5 abc 6 abc 7 abc 8 abc 9 abc 10
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If someone has globally modified the value of $, they deserve to be slapped with a trout, but a quick fix for you is to locally reset the value where its causing you problems:

{  # set up new enclosing scope since we are modifying globals
   local $,;            # temporarilly set $, back to the empty string
   print "<center><textarea name=head rows=6 cols=60 wrap=soft>\n";
   print @linesHead;    # <- wont see extra spaces here...
   print "</textarea></center>\n"; 
}  # end enclosing scope... $, is back to its old value
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-Blake