It worked!!!

Instead of dummy text, I wrote the original text in white color. The background is white. So the white text is not viewable in the pdf. Is it a bad idea?? Is there any other way instead of putting the original text?

$text->fillcolor('#ffffff');
$text->translate($x, $y);
($overflow_text, $height_remaining) = $text->paragraph(qq{text here}, 
+$width, $height);
[download]

$y is re-calculated with respect to $height_remaining.

$y -= $height_remaining / 2;
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Now I wrote the text again in black font. So now the text is vertically aligned in the given height.

$text->fillcolor('#000000');
$text->translate($x, $y);
$text->paragraph(qq{text here}, $width, $height);
[download]

Thanks again!!!