in reply to [Solved]: How to perform different actions before and after submit button is clicked.

To get the value of a form input you need to give it a name, so change your button to: 
<input type="submit" name="button1" value="Submit" />

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Then you can see if it was clicked: 
print '<html><head><title>Test</title></head><body>';

if ( $query->param('button1') ) {
    print 'Thank you - your form was submitted correctly!';
}
else {
    print '<form method="post"><input type="submit" name="button1" val
+ue="Submit"></form>';
}

print '</body></html>';

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