Remove last letter of first name (if it contains 's' or 'ς') and display it in email

removelastletter.html

{% capture name %}{{recipient.first_name}}{%endcapture%}

{% assign size = name | size | minus: 1 %} 

{% capture lastletter %}{{ name | slice: size, 1 }}{%endcapture%}

{% if lastletter == 's' or lastletter == 'ς'  %}
    {{ name | slice: 0, size }}
{%else%}
    {{recipient.first_name_or_friend}}
{%endif%}