Easiest way to substitute characters in the string
<p>Suppose I have a main form named "<code>main_form</code>" and I have few more forms name like "<code>w_main_form</code>","<code>g_main_form</code>" etc etc which are based on "<code>main_form</code>" and they vary according to the '<code>category</code>'.</p>

<p>Now is there any easy way to <em>generate</em> names of derived forms and how to call them.</p>

<p>Suppose the category is "<code>iron</code>" then the form name should be "<code>w_main_form</code>" and when the category is "<code>coal</code>" the form name should be "<code>g_main_form</code>".</p>
