You can search for a pattern at a specified location, such as the beginning or end of the string.
/^a/ Match against a only at beginning of string.
/a$/ Match against a only at end of string.
/a\b/ Match a at end of word.
/a\B/ Match a not at end of word.
/$a/ means to match the value of $a.
/a$/ matches against an a at the end of the string.
/$a$/ matches against the value of the variable $a at the end of the string.
The ^ character acts differently depending on whether it is inside a square bracket or not.
/^a/ looks for a at the start of the string.
/[^a]/ will return true if there is any character other than a anywhere in the word.