You can use hashcat to do so. You can write rules that will operate on your given wordlist (in this case, the single word "PleaseSub!") and generate a bunch of similar passwords according to your rules. e.g
sXY - s will replace X with Y
$X - will append the character X to your wordlist
^X - will prepend the character X to your wordlist
and so on, that link I provided will give you a bunch of different commands and how to utilise them effectively.
Example:
base_word.txt
PleaseSub!
please_sub.rule
se3 # Replace e with 3
sl1 # Replace l with 1
$1 # Append 1 to the generated password
$2 # Append 2 to the generated password
$3 # Append 3 to the generated password
Which can then be called like so hashcat --stdout -r please_sub.rule base_word.txt
Output
Pl3as3Sub!
P1easeSub!
PleaseSub!1
PleaseSub!2
PleaseSub!3
You can skip generating the wordlist and just call it directly like so hashcat -m <mode> hash.file base_word.txt -r please_sub.rule
Writing your own rules can be quite difficult, so a helpful hint if you're trying this on Kali there are a bunch of pre-built rules in /usr/share/hashcat/rules/
E.g.
hashcat -m <mode> hash.file wordlist.txt -r /usr/share/hashcat/rules/best64.rule