Bootstrap 4 checkbox checked is not checked

I would like to have checked checkbox in my website, but it dows not work.

The website is generated dynamically by perl, so this is a problem. If I want to display just a template without perl variables (I use {variable} for generating variables in a page), the checkbox is checked!! Does anybody know, how could I fix it?

I have a code like this:

<div class="form-check" style="margin-top:5px;">
   <label class="form-check-label" id="disableDHCPe" name="disDHCPe" style="padding-left:0px;">
       <input type="checkbox" class="form-check-input" checked> DHCP
   </label>
</div>

But if I run the website in browser, checkbox is not checked and code looks like:

<div class="form-check" style="margin-top:5px;">
   <label class="form-check-label" id="disableDHCPe" name="disDHCPe" style="padding-left:0px;">
   <INPUT type="hidden" name="disDHCPe" id="disDHCPe" value="">
   <INPUT type="checkbox" id="disDHCPe_chk" name="disDHCPe_chk" onchange="disDHCPe.value=this.checked?'X':'';"> DHCP</label>
</div>