The messages you receive tell exactly what's wrong:

Global symbol "$count" requires explicit package name at test.pl line 
+14.
Global symbol "$first" requires explicit package name at test.pl line 
+15.
Global symbol "$first" requires explicit package name at test.pl line 
+16.
syntax error at test.pl line 16, near ");"
Global symbol "$sum" requires explicit package name at test.pl line 18
+.
Global symbol "$count" requires explicit package name at test.pl line 
+21.
Global symbol "$sum" requires explicit package name at test.pl line 22
+.
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Define $count, $first and $sum, like the other variables in your script. For example, add the following line in the appropriate place:

Next, No semi colon required here:

if ($first=='H');
{
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Should be:

if ($first=='H')
{
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I suggest spending some time working on the basics:

• perlintro
• http://learn.perl.org
• http://perldoc.perl.org
• Browse the Tutorials section of this site.