cat

This value is concatenated to the given variable.

Parameter Position	Type	Required	Default	Description
1	string	No	empty	This value to catenate to the given variable.

Template:

{$articleTitle = 'Psychics predict world didn\'t end'}

{$articleTitle|cat:' yesterday.'}

output:

Psychics predict world didn't end yesterday.

see also cat in PHP Smarty documentation.